Stdlib: printf() — VM + AOT formatted stdout write (#3681)

[PurHur]

Summary

• Add printf() VM builtin (ext/standard/printf_.php) delegating format to VmSprintf, output via OutputBuffer, return byte length (php-src formatted_print.c).
• Add AOT/JIT lowering via __compiler_printf runtime (lib/AOT/runtime/superglobals_refresh.c) and JitPrintf; register in SelfHostBuiltinPolicy bundle allowlist.
• Compliance + AOT PHPT + PrintfBuiltinTest (VM return length + AOT stdout smoke).

php-src reference

• ext/standard/formatted_print.c — PHP_FUNCTION(printf)

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter PrintfBuiltinTest'
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter "VMTest.*printf"'
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter "AotTest.*printf"'

Check	Result
PrintfBuiltinTest (VM + AOT)	OK (3 tests)
VMTest.*printf	OK (3 tests)
AotTest.*printf	OK (3 tests)

Closes #3681

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